1. Field of the Invention
The present invention relates generally to an implantation device and, more particularly, but not way of limitation, to an implantation device designed for loading with a surgical implant and for subsequent delivery of the surgical implant. The implantation device uses jaws and a spacer to secure a surgical implant and allow implantation into a patient.
2. Description of the Related Art
Shape memory implants are commonly used in surgical procedures that require the reattachment or fusing of tissue or bone. Shape memory implants can be composed of shape memory material such as Nitinol that allows the shape memory implants to have a first final shape and the ability to transform into a second shape. The shape memory material gives the implants elastic properties in that they store mechanical energy and are subject to elastic (recoverable) deformation when they release the stored mechanical energy. The implants are mechanically deformed into their second shape and held in their second shape by instrumentation such that, upon release from the instrumentation, the implants elastically deform from their second shape into their first final shape.
In surgical procedures, the elastic property of shape memory implants is used as follows. Bones that require fixating are aligned, and the shape memory implant, which has been mechanically deformed to its second shape, is held in instrumentation and inserted between the bones. After insertion, the shape memory implant is released from the instrumentation, whereupon the shape memory implant elastically deforms to its first final shape such that the shape memory implant maintains the bones fixated together. Because the shape memory implants stores mechanical energy, it continuously applies force to the fixated bones as the shape memory implant transitions from the second shape to the first final shape, which aids in the healing process.
Shape memory implants require instrumentation to maintain them in their second shape and for insertion into tissue or bone. To facilitate a more efficient surgical procedure, it is beneficial to preload the shape memory implants onto the instrumentation prior to surgery. Preloading shape memory implants onto instrumentation has typically been a two-stage process. In the first stage, the shape memory implant loads onto a constraining device that allows the shape memory implant to be transported and shipped. In the second stage, the shape memory implant is transferred from the constraining device onto instrumentation, and the instrumentation allows the surgeon to implant the shape memory implant into a patient during a surgical procedure.
Transferring the shape memory implant from the constraining device to the instrumentation increases the risk that the shape memory implant may accidently detach from either the constraining device or the instrumentation during a surgical procedure. Often if the shape memory implant detaches, the shape memory implant must be discarded for sanitary or other reasons.
The instrumentation for maintaining the shape memory implants in their second shape is typically forceps or implant insertion devices designed to receive the implants in their second shape. Although potentially effective, forceps require the implant to be loaded into the forceps during surgery, which can be cumbersome and time consuming. In addition, forceps are large which hinders implantation of the shape memory implant into a patient during surgery. Furthermore, forceps can be expensive instruments that require cleaning and sterilization after each surgery.
Implant insertion devices other than forceps tend to be formed around the exact profile of the shape memory implant. This is accomplished by having the implant fit inside a passage that is substantially the same diameter as the shape memory implant. By using this method, the implant insertion device allows the shape memory implant to be preloaded prior to surgery. However, using an implant insertion device that substantially conforms to the profile of the shape memory implant can create several problems for a surgeon. First, this type of implant insertion device often makes removal of the shape memory staple after implantation problematic. In particular, the shape memory implant sticks to the implant insertion device due to the frictional engagement between the shape memory implant, which is trying to compress, and the passage of the implant insertion device, resulting in a more difficult surgical procedure and the potential for a less than satisfactory fixation of tissue or bone. Second, this type of implant insertion device results in an abrupt and sudden release of stored mechanical energy as the implant is removed from the device. This type of implant insertion device provides no method by which to slowly transition the stored energy in the implant from the implant insertion device to the bones that are being fixated. Finally, this type of implant insertion device can result in entanglement during release, in which the implant legs begin to compress upon release and make extraction of this type of insertion device more difficult.
Accordingly, an instrument that constrains a shape memory implant in its second shape, allows the shape memory implant to be preloaded prior to surgery, simplifies removal of the shape memory implant after partial implantation, and controls the rate of release of tension would be beneficial.